Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, leaving overhang for easy removal.

In a large mixing bowl, whisk together the Greek yogurt and sugar-free sweetener until smooth and creamy. Add the eggs one at a time, whisking well after each addition. Stir in vanilla extract.

In a separate bowl, whisk together cocoa powder, almond flour (or oat flour), baking powder, and salt until evenly mixed.

Gradually add the dry ingredients to the wet ingredients, stirring gently with a spatula until fully incorporated. Avoid overmixing.

Fold in sugar-free chocolate chips if using.

Pour the batter into the prepared pan and smooth the top. Bake for 22–28 minutes, or until the edges are set and a toothpick inserted in the center comes out with a few moist crumbs.

Remove from the oven and let the brownies cool completely in the pan before slicing. This step is essential for the best texture.